Thin wall combustion liners are used throughout the industry in commercial, industrial, and military gas turbine engine applications. The purpose of the combustion liner walls are to provide a pressure drop for mixing and burning of fuel and air inside the gas turbine. The hot air is then directed into the turbine by the liner wall contours. The pressure drop for mixing is provided by the cooling air circuits (holes and slots), the dome and fuel nozzle air swirlers, and the liner dilution holes.
Gas turbine engines have incorporated axially cut keyhole relief slots in the aft seal rings of the combustion liner to reduce the hoop stress. Conventional keyhole slot geometry on combustion liners includes a round or elliptical stop drill hole at the root or base of the slot. Combustion liner aft seal rings are known to suffer from cracks initiating at the keyhole relief slots. These keyhole slots are typically distributed circumferentially around the liner to reduce the hoop stress fight experienced in the combustion liner aft seal ring. However, the shape of the relief slot can tend to contribute to crack initiation and other fatigue cracks in the aft seal rings adjacent to the relief slot because of sharp geometric notches and associated high Kt's (stress concentrations) in the local high hoop stress field.
There is a continuing need for technology development relating to modifying relief slots so as to increase crack initiation and fatigue growth life of the region in the aft seal rings experiencing a high hoop stress. More specifically, there is a continuing need to develop an advanced geometry slot configured for moving the high Kt features of the slot out of a high stress region to specifically enhance component service life. The present invention satisfies this need in a novel and non-obvious way.